The invention describes a method for preparing porous materials and, more particularly, to a method for preparing materials with a controlled, asymmetric, three-dimensional porous structure.
Microporous, mesoporous, and macroporous materials have become ubiquitous, and play important roles in sensors, chemical and physical separations, catalysis, photonics, and quantum dot utilization, among other applications. Unfortunately, direct synthesis of such materials has been limited to a few chemical compositions, most commonly silicas, aluminosilicates and aluminophosphates. The ability to prepare such porous structures in other compositional phase spaces and with asymmetric structures would enable a marriage of physical and chemical control, leading to new applications and devices. Asymmetric or chiral porous nanostructured materials are rare, and would be useful in catalysis, separations and sensing sciences. The availability of such materials would have enormous impact on the chemical and petrochemical industries, as well as in sensors for chiral molecules, and non-linear optical devices. In particular, the chirality of a molecule can determine whether it is therapeutic, benign, or toxic in a physiological environment. For instance P(−) sarin and tabun are several orders of magnitude more toxic than their P(+) stereoisomers. The ability to discriminate on a molecular level between chiral enantiomers is of paramount importance for sensors, chem/bio-warfare agent remediation, and synthesis of pharmaceuticals, agro-chemicals, fragrances, and foodstuffs. However, the reliable detection and processing of specific chiral molecules remains a challenge. Gas-chromatography using chiral columns is typically used for identification of enantiomers or pre-concentration prior to processing, but column retention times are 10 s of minutes. Chiral sensors based upon layers of chiral organic species are useful for only one, or a limited number of compounds. Very few chiral catalysts and sorbents exist since nature constrains materials to symmetric structures. Chiral membranes are based on organic polymers, thus operation is limited to relatively low temperatures.
Prior art dictates that inorganic coatings are rigid materials; however ultra-thin coatings of nano/micro-porous materials can show flexibility. Flexion can potentially enable geometrically-controlled asymmetric/chiral coatings leading to versatile, fast-responsive sensor/catalyst/adsorber platforms operable at high temperature. Fabrication on piezoelectric substrates could enable tuning for specific molecules via electrical signal, or rapid scanning for a range of molecules.